Positron Emission Tomography (PET) is a functional imaging technique with potential to quantify the rates of biological processes in vivo. The availability of short lived positron-emitting isotopes of carbon, nitrogen, oxygen and especially fluorine allows virtually any compound of biological interests to be labeled in trace amounts and introduced into the body for imaging with PET. PET imaging can provide diagnosis for symptoms of disease such as cancer. Alzheimer's disease, head trauma, and stroke. Recent studies indicate that PET imaging can provide valuable insight in clinical management of HIV infected patients. One problem that is encountered in reconstruction of PET imaging is the distortions that are caused by non-uniform attenuation of 511 keV positron annihilation gamma rays by surrounding tissue. In order to gather attenuation maps with greater accuracy to address such distortions, dual mode imaging systems are being developed which combine nuclear medicine techniques (such as PET) with X-ray CT imaging. The goal of the proposed research is to investigate a new scintillation material for use in dual PET-CT systems. PROPOSED COMMERCIAL APPLICATION: PET, CT, nuclear physics, astronomy, diffraction, radiology, NDE, nuclear treaty verification, and bore-hole logging.